It essentislly supports your weight
Imagine sitting in a leather loveseat where nothing holds the cushion from falling down on the floor. That;s what the diaphragm does. Prevents the seat from making contact with the floor when there’s any weight on it.
Hmmmm … No wonder then it eventually “fatigued” in my case ( ][ ) … 
I wonder if Jaguar considered a person’s weight when they designed this model… it appears to be made for people up to 5’-10’ and less than 200 lbs in weight and contortionists
Convertible handles my 6’-0" body with just over 200 pounds seemingly well.
What color ? Rob Laughton has a Rogue interior for sale. I have black and some tan
So, it in effect is a kind of “sling” for the cushion? 
But the funny thing is it seems the cushion is still above “ground” level … When I go to move the seat back/forth it does so with the same ease as before … just now with the loose rubber diaphragm dragging beneath it … 
Yep, sounds pretty “Brit” to me … 
There’s some hogrings holding foam and leather in place, but you’re in the endgame now. Those seat are not long for this world.